stuart saich
TRANSCRIPT
-
7/27/2019 Stuart Saich
1/27
-
7/27/2019 Stuart Saich
2/27
-
7/27/2019 Stuart Saich
3/27
Typical grade recovery curves for a copper project
-
7/27/2019 Stuart Saich
4/27
Introduction
Target Audience for presentation/paper
Project managers
Financial managers
Objective
Demystify some of the issues
Provide some real simple rules of thumb
-
7/27/2019 Stuart Saich
5/27
Cerro Verde
Collahuasi
Escondida
El Salvador
Manto Verde
Frieda River
Golpu Wafi
Ernest Henry
Mount Isa Mines
Lady Loretta
Olympic Dam
Batu Hijau
Bozshakol
OOkiep
Konkola
MMH
El Pachon
El Morro
Antapaccay
Las Bambas
Black Mountain
Project experience listing
-
7/27/2019 Stuart Saich
6/27
Presentation overview
key issues to discuss
Sample selection philosophy
Prescriptive versus proactive testing The role of mineralogy
Rules of thumb
Test result validation or rejection
-
7/27/2019 Stuart Saich
7/27
-
7/27/2019 Stuart Saich
8/27
Composite based testing Geologists define perceived ore types based
on lithology, alteration, mineralogy, and
expected metallurgical performance
Individual lengths of drill core aligned with
assay distribution of deposit are selected
Single well blended composite prepared Optimization testing carried out on composites
Basic assumption is that all material selected
for each ore type actually belongs in the ore
type
Ore type selection is not verified based onmetallurgical performance
-
7/27/2019 Stuart Saich
9/27
Variability Based Testing
Initial assumption of ore types made bygeologists, based on lithology,
alteration, mineralogy
Variability samples (50-60) for each ore
type are selected to provide spatial
distribution Individual variability samples are tested
to evaluate metallurgical performance
Basic assumption is that variability
sample only belongs in the ore type
when metallurgical performance isvalidated
Ore types re-defined upon completion
of this type of testing
-
7/27/2019 Stuart Saich
10/27
Typical Results from Composite vs Variability
Testing programs
-
7/27/2019 Stuart Saich
11/27
Metallurgical Testing program
philosophies
Prescriptive
Typically procedural in nature
Scope defined in detail prior to start of testing
Typically completed on composites
Focused on optimization of parameters
Laboratory has little room to move
Proactive
General guidelines given to laboratory
Laboratory needs to understand the clients business
Testing conditions adapted to suit metallurgical response
-
7/27/2019 Stuart Saich
12/27
Met Testing Rules of thumb!
Commonly heard rules of thumb Grind only as far as required to achieve 40-60% liberation
Target Industry Standard concentrate grade
Typical rougher mass recovery should be 8-12%
Collect no material that is lower in grade then feed
Maximize valuable metal recovery, whilst minimizing mass
recovery
Use proven reagent scheme
Focus on elements because we cannot measure minerals on
line Four of these are valid, the other three lead to poor
results!
-
7/27/2019 Stuart Saich
13/27
Focus on mineralogy and liberation
Minerals float elements dont
Industry standard concentrate grade concept devalues
project potential when secondary minerals are present
Chalcopyrite - 34.6 % Cu
Bornite - 63.3 % Cu
Chalcocite - 79.8 % Cu
Covelite - 66.5 % Cu
At laboratory scale should target a concentrate grade
equivalent to 80-85% valuable mineral content.
Industry Standard appears to be around 28% Cu
-
7/27/2019 Stuart Saich
14/27
Difference in results
Prescriptive vs Proactive testingOpen circuit Cleaner
Tests
Red Prescriptive
Green Proactive
Shape of grade
recovery curve is anindication of how close
you are to optimum
conditions
Results are from a
project currently in
development in Peru
-
7/27/2019 Stuart Saich
15/27
Laboratory met testing execution Flotation is a highly complex, yet surprisingly simple process
The factors affecting flotation are highly inter-dependant
The only time that you can see whether good flotation is occurring is
by being there!
Using a prescribed metallurgical testing program, i.e proven reagent
scheme is a fallacy The laboratory technician needs the freedom (and training) to be
able to make decisions on the fly with regards key flotation
conditions i.e.:
Reagent dosages, Air flow rate, Pulp density
A proper variability based program could never be executed using aprescriptive program as the optimal conditions change for each
sample
-
7/27/2019 Stuart Saich
16/27
Key flotation testing stages
Primary grind and liberation analysis
Rougher testing
Concentrate liberation evaluation Regrind
Cleaner testing
Locked cycle testing
-
7/27/2019 Stuart Saich
17/27
Primary Grind and Rougher
flotation testing key objectives Extent of primary Grinding
Grind only as far enough to achieve 40-60% liberation
Rougher flotation is first upgrading stage
Typically target upgrading factor of 8-12 times head grade
Mass/copper recovery Mass recovery to concentrate should be 8-12%
If mass recovery is 20-40% then something is wrong
Kinetics
Rougher float time ~ 8-12 minutes
If using >20 minutes then not applicable for scale-up
Reagents/Conditions
Adjust according to visual flotation response achieved
Monitor results to confirm
-
7/27/2019 Stuart Saich
18/27
Concentrate liberation
evaluation Use optical mineralogy to see what you have generated
Gn
Gn
Ma
Cp
Rougher concentrate Scavenger concentrate
-
7/27/2019 Stuart Saich
19/27
Cleaner and LCT Testing objectives
Mineral losses in rougher flotation are typically in coarse
size fraction
Mineral losses in cleaner circuit are typically in ultra fine
fraction
Need to only re-grind those minerals that need it. Use
mineralogy to identify correct target regrind
Avoid generating slow floating fines that compete with
pyrite
Avoid inducing excessive circulating loads
-
7/27/2019 Stuart Saich
20/27
Cleaner flotation testing
-
7/27/2019 Stuart Saich
21/27
Locked cycle testing
Initially thought of as method to emulate re-circulating
load in real world plant
Would typically expect LCT result to achieve 1-2 %
increased recovery over open circuit cleaner tests at
same concentrate grade
Seems to be used as a catch all to get perceived
reasonable grade and recovery for financial analysis
LCT results analysis methodology, and subsequent
decision process as to whether to reject test results does
not appear to well understood
-
7/27/2019 Stuart Saich
22/27
The LCT Test and objectives
-
7/27/2019 Stuart Saich
23/27
Typical LCT ResultsThe significant shift in
grade and recovery for
the LCT tests is a
major concern and
implies that correct
conditions for design
are not identified.
The question and key
is to find out why!
-
7/27/2019 Stuart Saich
24/27
Unstable LCTs - Do these exist?
Note the following:
1. The first stage generates
results similar to that of the
open circuit cleaner test
2. From then on recoveryincreases
3. Three stable tests are not
achieved, and the difference
between the first and last
cycles are too big
4. Any LCT that looks like thisshould be rejected and not
used for design or financial
evaluation purposes
-
7/27/2019 Stuart Saich
25/27
This stream is the
culprit. It represents
middlings particles
that were not fully
liberated in regrind
and now need to
return for a 2nd, 3rd, 4th5th etc time around
-
7/27/2019 Stuart Saich
26/27
Conclusions Part I
The sample selection philosophy and testing program
may well have an impact on metallurgical results
obtained
The use of either prescriptive or proactive met testing
philosophy and management will probably have a
significant impact on results obtained
A focus on elements only and not mineralogy would
probably result in lower concentrate grades being
accepted
Be very careful of Rules of thumb Some are not good!
-
7/27/2019 Stuart Saich
27/27
Conclusions Part II If the met testing program does not provide sound data for design,
then the basis for that projects development will always be sub-
optimal
In reality flotation is a very forgiving process and operators tend to
adapt to what they are given to work with ->
However the selection of mechanical equipment and specification of
design criteria that is based on sub-optimal results means that the
project will probably operate at a lower overall efficiency than what it
really could for the life of the mine